… processes. Source: jzehnder / fotolia.com Nickel belongs to the heavy metals and usually occurs bound to other substances. In ambient air arsenic is measured … vapors may cause a degeneration of the nasal mucosa, asthma and pneumoconiosis. But for the general population Nickel is known to be a contact allergen. Nickel … are classified to be cancerogenic, metallic Nickel is probably cancerogenic. Air quality standards There is an Europe-wide target value of 20 ng/m³ as annual mean …